FIELD OF THE INVENTION
The present invention relates to N.sup.G -protected.sup.G -protected-L-argininal-di-lower alkyl acetals represented by formula (I): ##STR1## wherein X represents a protective group for a guanidino group; Gu represents a guanidine residue; and R represents a lower alkyl group, and salts thereof. The present invention also relates to L-argininal-di-lower alkyl acetals represented by formula (II): ##STR2## wherein R represents a lower alkyl group, and salts thereof, and a process for production thereof as well as intermediates for synthesis thereof.
The N.sup.G -protected-L-argininal-di-lower alkyl acetals (I) and L-argininal-di-lower alkyl acetals (II) of the present invention are useful as starting materials for N-terminal-protected or unprotected-peptidyl-L-argininal-di-lower alkyl acetals which are starting materials for various protease inhibitors and ligands used for affinity chromatography of various proteases.